Versatile System for Dual Carrier Transformation in Orthogonal Frequency Division Multiplexing

Abstract

The present invention provides a versatile system for selectively spreading carrier data across multiple carrier paths within an Orthogonal Frequency Division Multiplexing (OFDM) system (200), particularly an ultra-wideband (UWB) system. The present invention provides a data input (202), which passes data to a randomizer (204). The data then passes to a convolutional code function (206), the output of which is punctured by puncturing function (208). An interleaver function (210) receives the punctured code data, and cooperatively operates with a mapper element (218) to prepare the coded data for pre-transmission conversion by an IFFT (220). The mapper element (218) comprises a dual carrier modulation function (216), which associates and transforms two punctured code data elements into a format for transmission on two separate signal tones.

Description

PRIORITY CLAIM[0001]This application is a divisional of U.S. application Ser. No. 11 / 099,317 filed Apr. 5, 2005 which claims priority to U.S. Provisional Application No. 60 / 559,845, filed Apr. 6, 2004. This application has inventors-in-common and is assigned to Texas Instruments Incorporated—assignee of U.S. patent application Ser. No. 10 / 688,169.TECHNICAL FIELD OF THE INVENTION[0002]The present invention relates generally to the field of wireless communications and, more particularly, to structures and methods for maximizing utilization and efficiency of communications utilizing orthogonal frequency division multiplexing through frequency domain transformations.BACKGROUND OF THE INVENTION[0003]Increasing demand for more powerful and convenient data and information communication has spawned a number of advancements in communications technologies, particularly in wireless communication technologies. A number of technologies have been developed to provide the convenience of wireless c...

AI Technical Summary

Benefits of technology

[0012]The present invention provides a versatile system, comprising various structures and methods, for optimizing the utilization, efficiency, and reliability of OFDM-based communications, through selective frequency domain transformation prior to transmission. The system of the present invention provides a frequency domain transformation for a group of signal sub-carriers, prior to transmission, in a manner that effectively spreads sub-carrier energy across a group of sub-carriers. The present invention is readily adaptable to a number of design requirements and variables, and may be implemented in a variety of OFDM-based systems. The present invention thus provides optimal data throughput in OFDM-based communications in an easy, cost-effective manner.

Problems solved by technology

Since wireless communications rely on over-the-air (OTA) transmissions, wireless systems and their operation are subjected to a number of environmental interferences, as well as regulatory requirements and restrictions.

These regulatory influences can vary considerably, and even conflict, across different countries or regions.

This UWB frequency allocation is unlicensed, leaving the spectrum open to a number of potentially conflicting technologies.

Due to this unlicensed nature, UWB devices and systems have to contend with both pre-existing and future-developed services that occupy adjacent frequency bands or share some portion of the same frequency band.

Moreover, the relative strength (i.e., power) of UWB signals is also limited to a transmit power of −41.25 dBm / MHz.

Due to this relatively low-power, short-range nature of UWB, even a nominal degree of signal fading or interference from an adjacent frequency band can significantly impact the signal integrity of a given tone.

In the increasingly common situation where a conventional OFDM system (e.g., a UWB system) must account for one or more spectral masking requirements, certain sub-ranges of a frequency band cannot be utilized—decreasing the system's potential data transfer bandwidth.

Unfortunately, however, conventional OFDM systems utilize a number of data coding and redundancy techniques for error correction and data integrity purposes.

Although these techniques improve the reliability and integrity of data transmissions, by accounting or correcting for signal noise or interference, they reduce effective data transfer bandwidth by significant amounts.

Thus, wireless system designers utilizing OFDM techniques may often face a tradeoff between achieving optimally high data transfer rates and ensuring data integrity or reliability.

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